The proposed research focuses on the social ecology of institutional and community-based residential environments for retarded children and adults. The primary objectives are: (1) to evaluate the effectiveness of alternative treatment strategies to promote positive interaction between retarded individuals and their environments, and (2) to test the validity of a set of hypotheses about how to "match" individuals and environments. Three prospective and observational studies will be conducted on 552 subjects in 69 environments. Study #1 evaluates alternative treatment strategies to improve the quality of institutional life. Study #2 is a pre-post test of subjects placed in specialized community group homes versus institutional controls in small, enriched living units, Study #3 constitutes an experimental test of the practical utility of the principles associated with the proposed model of "person-environment fit". For subjects who are poorly matched to their environments, specific changes -- theoretically designed to encourage positive adaptation -- will be introduced and assessed. The significance of this research relates to its potential for advancing knowledge about what comprises optimal residential environments for retarded individuals.